1. Field of the Invention
The present invention relates to a recording apparatus for attaching a recording material onto a recording medium so as to record an image and, more particularly, a recording apparatus which can record on different types of recording medium.
2. Description of the Prior Art
In a recording apparatus, recording quality is greatly affected by the physical properties of the recording medium.
For example, in an ink-jet printer, the use of special paper is recommended. When such special paper is used, good printing quality is obtained.
The recommended paper must satisfy various conditions in, for example, diffusion isotropicity, diffusion speed, adsorption speed, and reflection density of printed ink droplets. When printing is performed by mounting a light-transmitting recording medium such as a film for an overhead projector (to be referred to as an OHP hereinafter) on such a printer, the printing quality may be significantly degraded depending upon the properties of the recording medium. In the worst case, the printed ink may not be fixed. In view of this problem, it has been proposed to perform a surface treatment of the OHP film to form a thin film of gelatin or PVA, and so improve the fixing performance.
However, an improvement in the fixing performance does not necessary improve other properties of the OHP film. Moreover, this recording medium has a low printing density which is attributed to the differences in basic properties between this specially treated OHP film and normal paper.
More specifically, unlike paper, OHP film exhibits low diffusion property (i.e., low dot extension). And improving fixing property means a decrease in diffusion property in the case of the OHP film. Therefore, when such an OHP film is used with a conventional ink-jet printer, each pixel dot becomes small, resulting in a low printing density with too bright portions. As shown in FIG. 2, a dot diameter 3 ejected onto a one-pixel area 1 is smaller than a dot diameter 2 on normal paper as shown in FIG. 1.
OHP films transmit light. However, the conventional recording medium expresses an image pattern with reflected light therefrom. When a comparison is made between a reflected light density from an image printed with an ink having a relatively low ink density but colored in an overall pattern (each ink dot is diffused to reduce the background area), and a transmitted light intensity from an image printed with an ink having a not so low ink density but a relatively wide dot interval and a small dot diameter, the former may appear darker to the human eye.
In order to increase the printing density, the dye content may be increased. However, an increase in the dye content gives rise to problem of clogging of a head channel and the like after a long non-printing period, segregation of the dye and the like. In view of these problems, the dye content cannot be increased above a predetermined level.
A method has been proposed improving printing density on an OHP film by ejecting ink a plurality of times. However, when this same method is adopted for normal paper, due to ejection of a large amount of ink, various other problems are caused including a decrease in resolution, flow of ink, and formation of wrinkles in the paper. Furthermore, since a plurality of ejection operations are performed for each pixel, the recording speed is lowered.